Air conditioning system



Mmh ,1938. D. w. MCLENEGAN 112,038

AIR CONDIT IONING SYSTEM Filed May 5, 1936 2 Sheets-Sheet 1 Fig. l.

Ihvento'r'z" David ml. Mc Lehegan,-

His Attorney- March 22, 1938. D. w. MOLENE AN 2,112,038

7 AIR CONDITIONING SYSTEM 7 Filed May 5, 1936 2 Sheets-Sheet 2 Inventor:David \A/. Me Lenegan,

b fi/MZ g j? is Attorngg.

Patented Mar. 22, 1938 CONDITIONING sys'rEM David W. McLenegan,Caldwell, N. .l., assignor to General Electric Company, a corporation ofNew York Application my 5, 1936, Serial No. we

9 1 r 1 II 5.

My invention relates to air conditioning systems for cooling anddehumidifying the air within auditoriums, rooms and other enclosures.

It is an object of my invention to provide a system for cooling anddehumidifying the air within an enclosure including a cooling coil andan. improved arrangement for readily changin the supply'of coolingmedium to vary the effective cooling surface of the coil in accordancewith the temperature and humidity conditions of the air in theenclosure.

Another object of my invention is to provide a system for cooling anddehumidifying the air within an enclosure including a cooling coil and.15 having a thermostatically operated valve for controlling theadmission of refrigerant to the cooling coil and an arrangementforvarying the ambient surrounding the control bulb of the valve to varythe length of the portion of the coil containing superheatedrefrigerant'vap'or.

Further objects and advantages of my invention will become apparent'asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to theaccompanying drawings in which Fig. l is a diagrammatic illustration ofan air conditioning system embodying my invention; Fig. 2 is an enlargeddetail view of the thermostatic bulb and heating coil therefor shown inFig. 1; Fig. 3 is a sectional view on the line 3--3 of Fig. 2; and Fig.4 is e. sectional view of a modified form of the bulb and heater, shownin Referring now to the drawings, in Fig. 1 I have shown an airconditioning system comprising a I casing I0 arranged to receive freshair through a duct I I and air from the room to be conditioned through aduct I2 which passes through a wall I3 of the room. The fresh air andthe room' air are mixed in the casing I0 and aredrawn therethrough byoperation of a fan I4 arranged at the discharge side of the casing. Theamounts of fresh air and room air admitted to the casing are determinedby adjustable dampers Ila and I2a, respectively. The conditioned air isretumedto the room through a duct I5 passing through 5 the wall I3. Afilter I6 is provided In the casing to remove dust and other impuritiesfrom the air, and the air is cooled by passing through a cooling elementI'I arranged in the casing and comprising a sinuous coil 18 having aplurality of 5 turns arranged in three banks extending entirely (cite-s)acrossthe casing in the path of the air. Coil I8 is preferably of thetype having a plurality of fins for providing a large heat absorbingarea. The coil I t is connected in the circuit of a mechanicalrefrigerating machine including a com- 5 pressor I9 driven by a motor20, a condenser 2i and a liquid receiver 22. Gaseous refrigerant iscompressed in the compressor It and is discharged into the condenser Mwhere it is cooled and liquefied by air circulated thereover by afan 2tdriven by a motor 2t connected across the motor W. The condensedrefrigerant collects in the liquid receiver 22 and is supplied tothecoil It by operation of an expansion valve 25. The refrigerant ispreferably admitted to the coil it 15 so that it flowsvthrough the banksIta, IBD, and

I 80 of the coil in succession in the opposite direction from that ofthe flow of air through the duct It. The air thus passes from the leastcold to the coldest portion of the coil. Refrigerant 20 vapor iswithdrawn from the coil 58 through a conduit 21 and is returned to thecompressor It; The valve 25 is of the well known thermostaticallyoperated type and is provided with a thermostatic element such as a bulbcontaining a 25 volatile liquid and mounted in heat exchange relationwith the suction side of the coil I8. The bulb is connected with a valveoperating bellows in the valve casing through a tube 26, in order tocontrol the admission of refrigerant to the coil 30 w, in response tothetemperatureof the gaseous refrigerant withdrawn from the coil.

The refrigerating machine is controlled by a thermostat 28 having arelay 28a and being responsive to the temperature of the air in the 5room and bya humidostat 29 having a relay 29a and being responsive tothe relative humidity of the air in the room. The thermostat 28 isarranged to control a switch 80 in the power supply line of the motor20. Should the humidity of 40 the air in the room he abnormally high thetemperature of the air in the room may be reduced sufficiently tosatisfy the thermostat 28 before the humidity has been reduced thedesired amount to provide maximum comfort for the occupants 5 oftheroom. In such cases it is desirable further to dehumidify the air,but 'any substantial decrease of the temperatureof the air in the roommust be avoided in order to maintain a comfortable temperature ior theoccupants of the room. However, it may be permissible to continue thecooling action at a reduced rate in order that the humidity may befurther reduced.

In most air conditioned spaces some of the heat winch must be removed bythe air conditionin '55 system originates within the room itself. Forexample, occupants, electric lights, motors and other heat producingappliances and also the sun's rays entering through the windows, allgen- 5 erate heat within the room. It is necessary that the heat fromsuch internal sources be removed from the room before any reduction ofthe temperature in the room below that of the outdoor air can beaccomplished. It is evident, therefore, that part of the capacity of thecooling system must be devoted to the removal of heat from theseinternal sources. 'In air conditioning systems in which the internalheat of the space to be conditioned must be removed a small portion ofcooled air may be circulated continuously without reducing the totalsensible heat of the air in the space to be conditioned. It is possiblein such systems to produce a substantial amount of dehumidification withonly suflicient sensible cooling to offset the effect of the internalheat sources in the room so that dehumidification may be accomplishedwithout reduction of the dry bulb temperature of the air in the room.

If the thermostat 28 is satisfied due to the reduction of thetemperature of the air of the room to a predetermined low value beforethe humidity has been reduced to satisfy the humidostat 29, thehumidostat will take over the control of the motor 20 and continue theoperation of the motor until the humidostat is satisfied or until aminimum allowable temperature of the air in the room has been reached asdetermined by a low temperature limit thermostat 9i. When the motor isunder the control of the humidostat the supply of refrigerant to thecoil is reduced and consequently, an increased percentage of the totalcoil length is filled with superheated refrigerant gas. With the fiowof' refrigerant restricted the balance of heat transfer capacity betweenthe coil and the compressor is changed so that a lower refrigerantpressure is maintained in the coil. At this lower pressure thesaturation temperature of the refrigerant is lower and the surfacetemperature of the coil is, therefore, lower in that portion of the coilin which the gas is not superheated. The dehumidification-accomplishedby this cold portion of the coil is increased as compared with thedehumidification during the normal operation of that portion but thetotal sensible heat removed from the air by the coil is reduced.

The above described arrangement for effecting a control of temperatureand humidity by modifying the operation of the refrigerant supplycontrolling device in accordance with the humidity of the air in anenclosure is not'my invention, but is the invention of Edward W.Roessler, and is described and claimed in his copending applicationSerial No. 77,949, filed May 5, 1936, and assigned to the GeneralElectric Company, assignee of my present invention;

When it is desired to operate the air conditioning system illustrated inFig. 1, electric energy is supplied to lines 32 and 33. This energizes atransformer 34 having a primary winding 35 and a secondary winding 36.If the temperature of the air in the room rises to a predetermined valuea bimetallic strip 31 of the thermostat 28 engages a contact 38 andcloses a circuit from one side of the secondary 36 through a connection39, the strip 31 and a connection 49 td a coil M of relay 28a and thenceback to the other side of the secondary 36 through a connection 42 and aline 43. The coil 4! will thereby be energized and will pick up anarmaaiiaose ture M of the relay 28a, raising arms 15 and M of the relayinto engagement with contacts ll and it, respectively, and breakingengagement between the arm 49 and a contact 9. The raising of arm 46closes a holding circuit for the coil ill through connections 50 andiii, thereby maintaining the coil energized even though the strip 37should move out of engagement with the contact 38. The raising of thearm closes a circuit of a coil 52 of the switch 39 from line 32 througha connection 53, arm 35, a line H to the coil and thence back to line 33through a connection 55. The energization of coil 52 picks up anarmature 56 of switch 30 thereby closing the switch and connecting motorleads 5! and 59 to lines 32 and 33, respectively. The motor is thusenergized to operate the compressor l9 and supply refrigerant to thecoil Ill. The operation of the motor will continue until a predeterminedlow temperature of the air in the room has been reached when thebimetallic strip 9'! will engage a contact 59. This short-circuits therelay coil M through connections 42 and till, strip 91 and connection40, thereby deenergizing the coil and causing relay 28a to drop out andbreak the circuit of coil 52 to open switch The motor 2|] is therebydeenergized and the supply of refrigerant to the coil Ill discontinued.

When the air conditioning system is operating as just described thevalve 25 is set to maintain a minimum temperature of the refrigerantwithdrawn from the coil l8. In other words, a minimum length of the coilis maintained filled with superheated refrigerant vapor while the majorportion of the coil contains saturated vapor and liquid refrigerant andis effective for dehumidifying the air passing over the coil and forsubstantially reducing the sensible heat of the air inthe room It hasbeen pointed out above that by operat ing only a portion of the coolingcoil at low temperature, while the remaining portion containssuperheated refrigerant vapor, the humidity may be decreased withoutsubstantially decreasing the sensible heat of the air in the room. Thisfurther reduction of humidity is accomplished, as has already beenstated, by arranging the room humidostat so that it will take overoperation of the refrigerating machine in the event that the humidity isstill too high after the room thermostat issatisfied. I, therefore,provide a small heating coil adjacent the thermostatic element or bulbof valve 25 in order to vary the temperature of the bulb and. modify itscontrol effect. Under normal operating conditions in response to theroom thermostat this heater is maintained energized so that only arelatively small amount of heat need be supplied to the bulb from therefrigerant withdrawn Electric Company, the assignee of this presentapplication.

When the control of the refrigerating system is taken over by thehumidostat the heating coil is deenergized and all the heat applied tothe control bulb necessary to operate the valve 25 must be received fromthe refrigerant withdrawn from the coil I8. The vapor withdrawn from thecoil l8 must now attain a higher temperature bulb of the expansion valve5 are connected in a circuit including a varia le resistor 84, an arm 85of relay 28a andthe arm 48 of relay 2811.

This circuit is closed whenever relay 28a is ener"-'.:-

g'ized by the room thermostat to raise the arm 45. It is, therefore,energized whenever the control of the refrigerating machine is takenover by the room thermostat. Whenever the arm 85 is raisedin response tooperation of the room humidostat 28 the heating coil is deenergized and,therefore, a minimum length of the cooling coil is utilized fordehumidifying whenever the refrigerating machine is operated in responseto the humidostat. Thelength of the portion of the coil l8 which ismaintained filled with superheated refrigerant vapor during normaloperation of the refrigerating machine may be varied-by adjusting therheostat- 84 so that if desired the normal rate of cooling may be variedthereby.

In. Figs. 2 and ,3, I have indicated at 86 the bulb of the thermostaticexpansion valve 25.

This bulb is secured in good heat exchange re- -latinship to the suctionside of the coil in any suitable manner, such as by soldering asindicated at. The heater previously referred to comprises an insulatedheating wire "secured closely about the bulb 88 by spring clips 88. Ends.18 and ii of the heater 88 are secured to the terminals 6| and 62 inany suitable manner, and the cover 88 which comprisesa block ofinsulating material completely surrounding the bulb 88 and adjacentportions of the cooling coil l8 holds the heating wire 88 in contactwith the bulb 88. Whenever the circuit of the heating wire 88 is closedand the wire heated the temperature of the" bulb 86 is raised and acertain amount of liquid is vaporized therein, thereby changing thepressure in the bellows of the expansion valve; when the circuit isopened the bulb 88 quickly cools down to the temperature of the coil i 8adjacent thereto. Should it be desired to delay the heating effect ofthe wire 88 after the wire is energized a body of metal may be providedbetween the wire and the bulb which will have a heat storage effect. InFig. '4 I have shown the thermostatic bulb 68 provided with a body ofmetal i8 secured to the 'bulb' between the bulb and the heater 88, inorder to obtain this flywheel?- or heat storage effect.

During the operation of the air conditioning system shown, should thehumidity of the room still be above the desired value after thethermostat 88 has been satisfied, the humidostat 88 will be in positionto control the motor and the relay 28a. will operate to deenergize theheating wire 88 and to continue the operation of the refrigeratingmachine. When the humidity is too high a movable member 18 of humidostat88 is in engagement with a contact I8 establishing a circuit.

from one side of the secondary 88, through-the connection 8i, arm 88 ofrelay Maya line l5; a

v and an arm 82, thereby breaking'the circuit of the heating coil 88 andclosing a holding circuit for the coil 88 from line 15 through arm 82and a connection 88 to maintain the relay 28a in its raised positioneven though the movable member I3 moves out of engagement with thecontact 14. .In its raised position the arm 85 engages a contact 84closing a circuit from line 32 through a connection 85, arm 65, aconnection 88 and line 54 to coil 52 and thence to line 33 through the.connection 55 thereby energizing coil 52 and operating switch 38 tocontinue operation of the motor 28 of the refrigerating machine andsupply refrigerant to the coil l8. Since the heating wire 88 is nowdeenergized a greater amount of heat must be received by the bulb 88from the vapor withdrawn from 'the coil l8 in order to actuate the valve25 and, consequently, the vapor in a greater portion of the coil i8 ismaintained superheated, and a smaller p'ortion of the coil is availablefor operation at a low temperature to'dehumidify the air passing throughthe casing l8. Since a larger portion of the coil is maintained fllledwith superheated refrigerant vapor the temperature of the air passingthrough the casing i8 will'not be decreased as much as during normaloperation of the system. However, since a portion of the coil is stillmaintained at a low temperature some moisture will be ab stracted fromthe air and-the air will be further dehumidified without substantialdecrease in the sensible heat of the air in the room.

The operation of the refrigerating machine under control of thehumidostat will "continue until the humidity has been reduced to adesired amount or until the temperature of the air has reached a minimumpermissible value consistent with comfort. Should the humidostat besatisfied the movable member 13 will engage a contact 81 therebyshort-circuiting the coil 88 through connection I9, strip I8, movablemember l8 and a portion of line 88, thereby causing relay 29a to dropoutand discontinue operation of the motor 28 by deenergizing coil 52 andopening switch 88. Should the temperature of the air in the room reachthe minimum permissible temperature bewill engage a contact 88 andshort-circuit the coil 88 through connection i8, strip 18 and a 1connection 88, thereby deenergizing the relay 29a and stopping theoperation of the refrigerating machine. Should the temperature of theroom for some reason increase until the thermostat 28 calls for cooling,'the control of the refrigerating machine will be transferred from thehumidostat 88 to the thermostat 28, since the operation of thethermostat will raise the arm 88 of the relay 88a thereby breaking thecircuit to humidostat 88 eausing the relay 28a to drop out and therebyagain energizing the heating coil 88 through the arm 88. ,Thecontrol ofthe system in re-' sponse to the room thermostat, therefore, takesprecedence over the control in response to the humidostat. r

It will be apparent from the foregoing that I have provided an airconditioning system for regulating, both the temperature and humidity ofthe air within an enclosure andincluding a simple and improvedarrangement for varying the efi'ective cooling surface of therefrigerating coil.

While I have disclosed a particular embodiment of my invention, variousmodifications will occur to those skilled in the art and I do not,therefore, desire my invention to be limited to the construction shownand described and I intend in the appended claims to cover allmodifications thereof which do not depart from the spirit and scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

l. A system for conditioning the air within an enclosure including acooling element, means for supplying cooling medium to said element andfor withdrawing cooling medium from said element, a valve forcontrolling the supply of cooling medium to said element, meansresponsive to the temperature of the cooling medium withdrawn from saidelement for actuating said valve to maintain a predeterminedsubstantially constant temperature of the cooling medium withdrawn fromsaid element, said temperature responsive means including a temperatureresponsive element arranged in heat exchange relationship with theoutlet side of said cooling element subject to the temperature of thecooling medium withdrawn from said cooling element, and means responsiveto a condition of the air within said enclosure and arranged to vary thetemperature of said temperature responsive element for modifying theoperation of said temperature responsive means to maintain apredetermined diflerent substantially constant temperature of thecooling medium withdrawn from said element.

2. A system for conditioning the air within an enclosure including acooling coil, means for supplying liquid refrigerant to said coil andfor withdrawing vaporized refrigerant from said coil, a valve forcontrolling the supply of liquid refrigerant to said coil, meansresponsive to the temperature of the vaporized refrigerant withdrawnfrom said coil and actuating said valve for maintaining superheated thevaporized refrigerant in a predetermined length of said coil, saidtemperature responsive means including a temperature responsive elementsecured in heat exchange relationship with the outlet side of said coiland subject to the temperature of the vaporized refrigerant withdrawnfrom said coil, and means responsive to the humidity of the air withinsaid enclosure and arranged to vary the temperature of said temperatureresponsive element for ,modifying the operation of said temperatureresponsive means to maintain superheated the vaporized refrigerant in adifferent predetermined length of said 0011.

3. A system for conditioning the air within an enclosure including acooling coil, means for supplying liquid refrigerant to said coil andfor withdrawing vaporized refrigerant from said coil, a valve forcontrolling the supply of liquid refrigerant to said coil, meansresponsive to the temperature of the vaporized refrigerant withdrawnfrom said coil and actuating said valve for maintaining superheated thevaporized refrigerant in a predetermined length of said coil, saidtemperature responsive means including a bulb containing volatile liquidand secured in heat exchange relationship with the outlet side of saidcoil subject to the temperature of the vaporized refrigerant withdrawnfrom said coil, and means responsive to the humidity of the air Withinsaid enclosure and arranged to vary the temperature of'said. bulb formodifying the operation of said temperature responsive means to maintainsuperheated a predetermined different length of said coil.

4; A system for conditioning the air within an enclosure including acooling coil, means for supplying liquid refrigerant to said coil andfor withdrawing vaporized refrigerant from said coil, a valve forcontrolling the supply of liquid refrigerant to said coil, meansresponsive to the temperature of the vaporized refrigerant withdrawnfrom said coil for actuating said valve to maintain superheated'thevaporized refrigerant in a predetermined length of said coil, saidtemperature responsive means including a temperature responsive elementsecured in heat exchange relationship with the outlet side of said coilsubjectto the temperature of the vaporized refrigerant withdrawn fromsaid coil, means including a heating element for determining thetemperature of said temperature responsive element, means for energizingsaid heating element, and means responsive to the humidity of the airwithin said enclosure and arranged to vary the energization of saidheating element for modifying the operation of said temperatureresponsive means to maintain superheated the vaporized refrigerant in adifferent predetermined length of said coil 5. A system for conditioningthe air within an enclosure including a cooling coil, means forsupplying liquid refrigerant to said coil and for withdrawing vaporizedrefrigerant from said coil, a valve for controlling the supply of liquidrefrigerant to said coil, means responsive to the temperature of thevaporized refrigerant withdrawn from said coil and actuating said valvefor maintaining superheated the vaporized refrigerant in a predeterminedlength of said coil, said temperature responsive means including a bulbcontaining a volatile liquid and secured in heat exchange relationshipwith the outlet side of said coil subject to the temperature of theyelement, means including a valve for controlling the supply of liquidrefrigerant to said element, means including a thermostatic elementresponsive to the temperature of the vaporized refrigerant withdrawnfrom said cooling element for actuating said valve to maintain apredetermined substantially constant temperature of the vaporizedrefrigerant withdrawn from said cooling element, means including aheating element arranged adjacent said thermostatic element andmodifying the operation of said temperature responsive means formaintaining a predetermined difierent substantially constant tempera- Iture of the vaporized refrigerant withdrawn from said cooling element,and means for selectively controlling said last two means.

'1. A system for cooling the air within an enclosure including'a coolingelement, means for supplying liquid refrigerant to said element and forwithdrawing vaporized refrigerant from said element, means including avalve for controlling the supply of liquid refrigerant to said element,means including a thermostatic element responsive to the temperature ofthe vaporized refrigerant withdrawn from said cooling element foractuating said valve to maintain a, predetermined substantially constanttemperature of the vaporized refrigerant withdrawn from said coolingelement, means including a heating element arranged adjacent saidthermostatic element and modifying the operation of said tem peratureresponsive means for maintaining a predetermined different substantiallyconstant temperature of the vaporized refrigerant withdrawn from saidcooling element, a body of heat insulating material arranged about saidheating element and said thermostatic element, and

means for selectively controlling said last we" means. v

8. A system for cooling the air within an enclosure including a coolingelement, means for supplying liquid refrigerant to said elementvaporized refrigerant withdrawn from said element, means including aheating element for supplying heat to said thermostatic element,

means varying the energization of said heating element and modifying theoperation oi said temperature responsive means for maintaining apredetermined diderent substantially constant temperature of thevaporized refrigerant withdrawn from said cooling element, and meansincluding a body of heat conducting material ar ranged between saidthermostatic element and said heating element for delaying the efiect ofa change of energization of said heating element.

9. A system for cooling the air within an enclosure including a coolingelement, means for supplying liquid refrigerant to said element and forwithdrawing vaporized refrigerant from said element, means including avalve for controlling the supply of liquid refrigerant to said element,means including a thermostatic element respon sive to the temperature ofthe vaporized refrigerant withdrawn from said cooling element foractuating said valve to maintain a predetermined substantially constanttemperature of the vaporized refrigerant withdrawn from said coolingelement, means including a heating element for supplying heat to saidthermostatic element, means varying the energization of said heatingelement and modifying the operation of said temperature responsive meansfor maintaining a predetermined difierent substantially constanttemperature ofthe vaporized refrigerant withdrawn from said coolingelement, means including a body of heat conducting material arrangedbetween said thermostatic element and said heating element for delayingthe eflect of a change of energization of said heating element. and abody of heat insulating material arranged about said heating element andsaid thermostatic element.

